Freezing conditions are continuing to affect parts of the UK, as forecasters warn it could be facing the coldest night of the year.

A fourth day of wintry weather has caused widespread disruption, affecting flights, trains and ferries.

Yellow Met Office warnings for snow and ice have been extended until 11:00 GMT on Tuesday. Forecasters are predicting temperatures could hit -15C (5F).

Hundreds of schools are to stay closed for a second successive day on Tuesday.

The Met Office's weather warning covers Wales, Northern Ireland, parts of Scotland, the Midlands, London and the South East of England.

Clear skies overnight could lead temperatures to drop lowest in Wales and central England.

A low of -11.6C (11F) was recorded on Sunday night in Chillingham Barns, Northumberland, although Saturday was the coldest night of the year so far, reaching -12.4C.

BBC weather forecaster Steve Cleaton said hazardous conditions would continue in the coming days, although there would be less snow than at the weekend.

"A perishingly cold night is expected as we move through Monday evening into Tuesday, with another widespread and severe frost, and temperatures plummeting to below -10C across any snowfields," he said.

Dozens of flights were cancelled from Heathrow after crews and aircraft were left out of position by Sunday's problems. Passengers are advised to check before setting off for the airport

Travel expert Simon Calder estimated that 50,000 British Airways (BA) passengers were stranded at airports in the UK and around the world on Sunday. The airline said additional staff were rebooking customers on to the next available flights and offering hotel accommodation

The Port of Calais reopened after closing for a few hours on Monday afternoon. P&O Ferries is reporting delays of up to two hours on journeys between Dover and Calais. Ferry company DFDS also has delays on its services between England and France

Eurotunnel said services were now back to normal after some passengers suffered long delays overnight - the firm says conditions remain "very challenging"

Motoring bodies the AA and RAC are warning drivers to adjust to the conditions "by slowing down and keeping a good distance"

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